1) Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus which irradiates a subject, such as a living body, with an ultrasonic wave, receives an echo of the ultrasonic wave, performs three-dimensional (hereinafter, “3D”) scan, and which displays a desired tomographic image of the subject on a monitor screen using 3D region image data obtained by the 3D scan.
2) Description of the Related Art
Conventionally, an ultrasonic diagnostic apparatus which irradiates a subject, such as a living body, with an ultrasonic wave, spatially receives an echo of the ultrasonic wave, performs 3D scan on the subject, generates 3D image data on this subject using a plurality of pieces of two-dimensional (hereinafter, “2D”) image data obtained by the 3D scan, and which displays a desired tomographic image of the subject on a monitor screen based on the generated 3D image data has been developed. An operator such as a medical doctor or an apparatus operator operates the ultrasonic diagnostic apparatus to display the desired tomographic image of the subject on the monitor screen, which searches or observes a region of interest of the subject such as an affected site, e.g., a tumor or a characteristic site in a body cavity, which grasp a shape, a size or the like of this region of interest, and which performs medical treatments such as ultrasonic diagnosis on the patient.
As related techniques to such a conventional technique, there is known the following technique. According to Japanese Patent Application Laid-Open No. 7-155328 for example, if a plurality of pieces of 2D image data obtained as a result of a 3D scan on a subject are arranged three-dimensionally, then an imaginary cut plane is set on each of the 2D image data thus arranged, the pieces of 2D image data are interpolated, and a tomographic image of the subject on the cut plane is displayed on the screen. According to Japanese Patent No. 3325224 for example, an ultrasonic diagnostic apparatus includes a small-diameter probe inserted into a forceps channel of an endoscope, performs a 3D scan on a subject by moving forward or backward the probe inserted into a hollow portion of the subject using a dedicated drive, generates a longitudinal image of this subject or a tomographic image thereof in various directions based on a plurality of pieces of 2D image data obtained by the 3D scan, and displays the generated image on a monitor screen. In addition, if a plurality of measurement points are set on the tomographic image, then the ultrasonic diagnostic apparatus measures a geometric value of a measurement target region by the measurement points, e.g., a diameter, a perimeter, an area, or the like of an affected site or the like on a plane of an organ displayed on this tomographic image.
However, the conventional ultrasonic diagnostic apparatuses disclosed in Japanese Patent Application Laid-Open No. 7-155328 and Japanese Patent No. 3325224 have the following disadvantages. When each of these conventional ultrasonic diagnostic apparatuses interpolates the 2D image data obtained by the 3D scan, it is assumed that the respective pieces of 2D image data are arranged in parallel. Therefore, irrespective of a scan path of this 3D scan, the apparatus displays the longitudinal image or the tomographic image of the subject almost linearly on the monitor screen. As a result, the longitudinal image or the tomographic image of the subject displayed by the apparatus is often strained, as compared with an actual shape of the subject. If the operator uses this apparatus, it is difficult to obtain the longitudinal image or the tomographic image of the subject which accurately represents the actual shape of the subject, and properly grasp the shape, size, or the like of the region of interest of the subject such as the characteristic site or the affected site.
Furthermore, the ultrasonic diagnostic apparatus disclosed in Japanese Patent No. 3325224 operates and outputs the geometric value of the measurement target region by the measurement points designated by the operator on the tomographic image using the tomographic image generated based on a plurality of pieces of 2D image data arranged in parallel. Therefore, the apparatus often operates and outputs the desired geometric value of the designated measurement target region on the strained longitudinal image or tomographic image, as compared with the actual shape of the subject. As a result, when the operator uses this ultrasonic diagnostic apparatus, it is often difficult to accurately measure the geometric value such as the length, the area, or the volume of the region of interest such as the characteristic site or the affected site present in the actual subject. Consequently, even if using the geometric value, the operator often finds it difficult to properly grasp the shape, the size, or the like of this region of interest.